The present disclosure relates to a method and apparatus for cutting a workpiece. More particularly, it relates a method and apparatus for cutting battery electrodes using a laser.
It is known to provide batteries or cells for use in vehicles such as automobiles. For example, lead-acid batteries have been used in starting, lighting, and ignition applications. More recently, hybrid electric vehicles are being developed which utilize a battery (e.g., a lithium-ion or nickel-metal-hydride battery) in combination with other systems (e.g., an internal combustion engine) to provide power for the vehicle.
It is known to manufacture battery electrodes by coating active material on a conductor. Typically, the conductor is a metal conductive material or a composite material laminated with a metal conductive material. However, it would be economically advantageous to perform the coating process on a relatively large sheet of conductor in a continuous process. It would further be advantageous to fabricate relatively large pieces, often in the form of a long rolled sheet, of electrode material and subsequently cut them as desired.
It is known to use a blade to cut the conductor. However, the use of blades has limitations and drawbacks. Cutting with blades is often imprecise and unreliable, compromising the structural integrity and overall quality and performance of the electrode. Blade cutting of metals also frequently creates burrs that can result in short circuits in tightly packed battery cells.
It is also known to cut a substrate with a laser. Although laser cutting provides a more reliable cut, it also has drawbacks. Lasers use focused energy to rapidly melt the electrode, which can cause splattering of material from the cut zone to the surrounding electrode surfaces. Electrode material may also evaporate and recondense on the electrode surface. Because electrodes are tightly packed together, pieces of slag from the cut zone extending outward from the electrode surface increase the risk of short circuits between electrodes, which can lead to failure and overheating. Due to its relatively high temperature, the cutting debris can also melt and/or cover the active material creating a “dead spot” on the electrode surface (i.e., a location where electrochemical reactions cannot occur).
Accordingly, it would be advantageous to provide a method and apparatus for laser cutting that cleanly and precisely cuts electrodes and prevents cutting debris from being deposited on the electrode surface.